1. Field of the Invention
The present invention relates generally to a bumper for vehicles, primarily for automobiles, having a face member made of a synthetic resin. More particularly, the invention relates to a shock-absorbing bumper capable of effectively absorbing the shocks resulting from a relatively light collision of a vehicle moving at a relatively low speed, such as when the vehicle is being parked or positioned in a garage.
2. Description of Relevant Art
Recently, automobiles have been provided with bumpers made of a synthetic resin to reduce the weight of the vehicle body and also to reduce the manufacturing cost. However, when a bumper is formed entirely from a synthetic resin, the material for the bumper has to be selected from a limited assortment of synthetic resins having a high hardness, and the bumper is required to be constructed with an excessive thickness. Such known synthetic resin bumper is economically disadvantageous, and at the same time the construction of same unfavorably affects the shock absorbing performance of the bumper.
In order to facilitate a thorough understanding of the advantageous functioning of the bumper according to the present invention as described in detail hereinbelow, an exemplary bumper construction is schematically illustrated in FIGS. 8(A) and 8(B) of the accompanying drawings so as to emphasize some of the disadvantages which might be encountered in a bumper which does not incorporate the features of the present invention. In such exemplary shock absorbing bumper as illustrated in FIG. 8(A), a face member a is formed in a beam-like shape having a channel-shaped cross section, with the inside thereof being lined with a steel back plate b. Another exemplary shock absorbing bumper as illustrated in FIG. 8(B) includes a filler member c formed of a polyurethane resin or a honeycomb core installed within a space defined between the face member a and a back plate b.
In the case of the exemplary shock absorbing bumper shown in FIG. 8(A), the back plate b is immediately deformed at the time of collision of the bumper with a wall or the like, which is accompanied by permanent deformation of the synthetic resin face member, thereby adversely affecting the appearance of the shock absorbing bumper. Further, the face member will be greatly deformed due to inferior shock absorption, which is inherent in its construction.
In the case of the exemplary shock absorbing bumper shown in FIG. 8(B), the face member comprises merely a decorative member, and the shock of collision is received by the material forming the filler c. However, the exemplary shock absorbing bumper of this type is disadvantageous with respect to price and weight because the absorbing efficiency of the material forming filler c is inferior, i.e., the porous filler material is easily collapsed and solidified to thus render same incapable of absorbing shocks applied thereto. Thus, such shock absorbing bumper must be formed with large dimensions to provide a long shock absorbing stroke for the face member by providing a larger space for accommodating a larger amount of the filler material.
Each of the exemplary shock absorbing bumpers shown in FIGS. 8(A) and (B) is provided with ribs a' projecting inwardly from the upper and lower ends (only the upper end being shown in the drawings) of the respective face members, and the periphery of the back plate b is fastened to the ribs at several positions by means of bolts and nuts d. Accordingly, in forming the face member a, when separating the molded face member from the mold having grooves for molding the ribs, the molded ribs interfere with the mold. To facilitate the separation of the molded face member a from the mold, the ribs are required to be flexible, and accordingly are formed of a soft synthetic resin material, the rigidity of which is not satisfactory for face members. Further, such construction requires a number of bolts and nuts for assembling the shock absorbing bumpers, resulting in an increased number of parts and more complicated assembly procedures.
The present invention provides a shock absorbing bumper formed of a synthetic resin with a simplified construction employing a minimal number of parts, which is easily assembled and is provided with a sufficient rigidity and effective shock absorbing performance.